The present invention relates to solar lighting apparatus of the sun tracking type, and more particularly to a solar lighting apparatus of the type mentioned which has a power source chargeable by a solar cell.
Solar lighting apparatus are adapted for use with a skylight bore having an opening in the roof of a building and extending to the ceiling for admitting sunlight into the interior of the building where sunlight is not available. The apparatus has light reflecting means, which is provided at the upper end of the skylight bore for reflecting sunlight into the interior through the bore.
Solar lighting apparatus of the sun tracking type are known which comprise light reflecting means directed toward the sun and made rotatable to track the sun so as to achieve an improved light admission efficiency since the sun changes in position with time.
With the solar lighting apparatus of the sun tracking type, the light reflecting means is rotated by a motor as a drive source. The motor is so controlled that the reflecting means is thereby rotated to track the sun during the daylight hours from sunrise till sunset and is further directed after sunset toward the position of sunrise on the next day.
When used as a power source for the motor, the commercial power source requires wiring from an interior receptacle, hence a need for labor and time. Power sources of the solar cell type are therefore suitable to use. With the power source of this type, a capacitor is charged with electric power output from a solar cell and delivers an output voltage to a constant-voltage circuit, which supplies a constant voltage to a motor drive source or the like.
When the power source of the solar cell type is used, it becomes impossible to drive the motor if the power source is completely discharged due to a spell of rainy or cloudy weather which results in an insufficient amount of sunlight. If a capacitor of great output is used to hold the system stabilized, the apparatus becomes costly. Accordingly, the power consumption required for the overall system needs to be as small as possible.
The means for controlling the driving of the apparatus in preparation for an interruption of power supply from the power source is usually provided with a backup secondary cell. The control means has incorporated therein data required for causing the light reflecting means to track the sun, and the data includes information, for example, as to the latitude and longitude of the site of installation of the solar lighting apparatus. If such information is initialized, restoration of the system requires much labor. When a backup secondary cell of increased capacity is used to hold the system stabilized, the apparatus becomes more costly. For this reason, the secondary cell must be checked meticulously for the charged state.
An object of the present invention is to reduce the power consumption of the overall system of a solar lighting apparatus of the sun tracking type wherein a solar cell power source is used.
Another object of the invention is to ensure a specified amount of charge at all times by monitoring the charged state of a backup secondary cell for control means for use in the solar lighting apparatus of the sun tracking type wherein a solar cell power source is used.
To overcome the problems described above, the present invention provides a solar lighting apparatus of the sun tracking type for guiding sunlight into a building by using light reflecting means, the apparatus comprising the light reflecting means for reflecting sunlight, drive means for driving the light reflecting means, control means for controlling the drive means to orient the light reflecting means toward the direction of the sun, and power source means for supplying electric power to the drive means and the control means, the power source means comprising a main power source unit chargeable by a solar cell panel for supplying electric power to the drive means and the control means, and a backup secondary cell chargeable with the electric power from the main power source unit for supplying electric power to the control means, the control means comprising real time clock means for measuring time, and a CPU for calculating the direction of the sun based on data as to time measured by the clock means and controlling the operation of the drive means, and the CPU being switchable from a sleep mode to an active mode in operating state based on the time data from the clock means.
The CPU controls the operation of the drive means in accordance with the time data from the clock means when in the active mode and is thereafter switched to the sleep mode. Stated specifically, the main power source unit is electrically connected to the control means and the drive means by way of a main power source switch, and the CPU turns on the main power source switch to drive the drive means and move the light reflecting means upon finding that the present time is in a time zone for tracking the sun when in the active mode and is thereafter switched from the active mode to the sleep mode in operating state, or is switched from the active mode to the sleep mode in operating state without driving the drive means when finding that the present time is not in the time zone for tracking the sun.
The CPU checks the backup secondary cell for the amount of charge therein in the active mode, and can thereafter be switched to the sleep mode. Stated more specifically, a charging switch is provided between the main power source switch and the backup secondary cell, and the CPU checks the secondary cell for the amount of charge therein in the active mode, turns on the charging switch when detecting a value lower than a predetermined amount of charge and is thereafter switched to the sleep mode.
The secondary cell can be charged in preference to the operation of the drive means.
A memory for storing data as to the latitude and longitude of the location of installation of the solar lighting apparatus can be included in the real time clock means. In this case, the backup secondary cell may back up the real time clock means only.
With the solar lighting apparatus of the sun tracking type of the invention, the CPU is set in the sleep mode and is changed over to the active mode only when interrupted by the real time clock means in a specified cycle. In the active mode, the CPU is returned to the sleep mode when not in the sun tracking time zone, or the CPU controls the operation of the drive means as specified, checks the backup secondary cell for the amount of charge therein when in the sun tracking time zone, and is thereafter set in the sleep mode again. Thus, the control means and the drive means remain out of operation until the CPU is subsequently interrupted by the real time clock means. This reduces the power consumption of the overall system of the apparatus to a minimum essential level.
When an interrupt is made by the clock means in the specified cycle, the backup secondary cell is checked for the amount of charge therein and charged if the detected value is less than a predetermined level. Thus, the predetermined amount of charge can be retained in the cell at all times.